Activation studies with amines and amino acids of the α-carbonic anhydrase from the pathogenic protozoan Trypanosoma cruzi

An Update on Synthesis of Coumarin Sulfonamides as Enzyme Inhibitors and Anticancer Agents

Coumarin is an important six-membered aromatic heterocyclic pharmacophore, widely distributed in natural products and synthetic molecules. The versatile and unique features of coumarin nucleus, in combination with privileged sulfonamide moiety, have enhanced the broad spectrum of biological activities. The research and development of coumarin, sulfonamide-based pharmacology, and medicinal chemistry have become active topics, and attracted the attention of medicinal chemists, pharmacists, and synthetic chemists. Coumarin sulfonamide compounds and analogs as clinical drugs have been used to cure various diseases with high therapeutic potency, which have shown their enormous development value. The diversified and wide array of biological activities such as anticancer, antibacterial, anti-fungal, antioxidant and anti-viral, etc. were displayed by diversified coumarin sulfonamides. The present systematic and comprehensive review in the current developments of synthesis and the medicinal chemistry of coumarin sulfonamide-based scaffolds give a whole range of therapeutics, especially in the field of oncology and carbonic anhydrase inhibitors. In the present review, various synthetic approaches, strategies, and methodologies involving effect of catalysts, the change of substrates, and the employment of various synthetic reaction conditions to obtain high yields is cited.

Amine- and Amino Acid-Based Compounds as Carbonic Anhydrase Activators

After being rather neglected as a research field in the past, carbonic anhydrase activators (CAAs) were undoubtedly demonstrated to be useful in diverse pharmaceutical and industrial applications. They also improved the knowledge of the requirements to selectively interact with a CA isoform over the others and confirmed the catalytic mechanism of this class of compounds. Amino acid and amine derivatives were the most explored in in vitro, in vivo and crystallographic studies as CAAs. Most of them were able to activate human or non-human CA isoforms in the nanomolar range, being proposed as therapeutic and industrial tools. Some isoforms are better activated by amino acids than amines derivatives and the stereochemistry may exert a role. Finally, non-human CAs have been very recently tested for activation studies, paving the way to innovative industrial and environmental applications.

Quantum mechanical study on the activation mechanism of human carbonic anhydrase VII cluster model with bis-histamine schiff bases and bis-spinaceamine derivatives

The activation mechanism of human carbonic anhydrase (hCA) isoform VII, hCA VII, with histamine, histamine bis-Schiff bases and bis-spinaceamine derivatives has been investigated using quantum mechanical calculations. The DFT-D3 method has been employed to calculate in detail the electronic structure and electronic energy of different compounds and complexes throughout the reaction pathway. The model system of hCA VII included the core catalytic center, the Zn²⁺ ion, its three histidine ligands and a hydroxide ion or water molecule coordinated to it. Furthermore, Thr199, Glu106 and the deep water molecule were considered in the model. Five activators of this enzyme, including histamine as standard, in complex with the cluster model of hCA VII were investigated. Thermodynamic functions for the overall reaction and for the complexation between activators and hCA VII were evaluated. Our results demonstrate that the protonatable moiety of these activators participates in proton transfer reactions from the zinc-bound water molecule to the reaction medium, promoting the formation of the catalytically active zinc hydroxide species of the enzyme. The QM analysis revealed that the electrostatic interactions between activators and hCA VII are the driving force of the enzyme-activator complex formation.

Carbonic Anhydrases: Versatile and Useful Biocatalysts in Chemistry and Biochemistry

Metalloenzymes such as the carbonic anhydrases (CAs, EC 4.2.1.1) possess highly specialized active sites that promote fast reaction rates and high substrate selectivity for the physiologic reaction that they catalyze, hydration of CO2 to bicarbonate and a proton. Among the eight genetic CA macrofamilies, α-CAs possess rather spacious active sites and show catalytic promiscuity, being esterases with many types of esters, but also acting on diverse small molecules such as cyanamide, carbonyl sulfide (COS), CS2, etc. Although artificial CAs have been developed with the intent to efficiently catalyse non-biologically related chemical transformations with high control of stereoselectivity, the activities of these enzymes were much lower when compared to natural CAs. Here, we report an overview on the catalytic activities of α-CAs as well as of enzymes which were mutated or artificially designed by incorporation of transition metal ions. In particular, the distinct catalytic mechanisms of the reductase, oxidase and metatheses-ase such as de novo designed CAs are discussed.

Tellurides Bearing Sulfonamides as Novel Inhibitors of Leishmanial Carbonic Anhydrase with Potent Antileishmanial Activity

We report for the first time a novel series of tellurides bearing sulfonamide as selective and potent inhibitors of the β-class carbonic anhydrase (CA; EC 4.2.1.1) enzyme expressed in Leishmania donovani protozoa. Such derivatives showed high activity against axenic amastigotes, and among them, compound 5g (4-(((3,4,5-trimethoxyphenyl)tellanyl)methyl)benzenesulfonamide) showed an IC₅₀ of 0.02 μM being highly selective for the parasites over THP-1 cells with a selectivity index of 300. The in vitro and in vivo toxicity experiments showed compound 5g to possess a safe profile and thus paving the way for tellurium-containing compounds as novel drug entities.

Activation of human α-carbonic anhydrase isoforms I, II, IV and VII with bis-histamine schiff bases and bis-spinaceamine substituted derivatives

A series of histamine bis-Schiff bases and bis-spinaceamine derivatives were synthesised and investigated as activators of four human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic hCA I, II and VII, and the membrane-associated hCA IV. All isoforms were effectively activated by the new derivatives, with activation constants in the range of 4.73–10.2 µM for hCA I, 6.15–42.1 µM for hCA II, 2.37–32.7 µM for hCA IV and 32 nM–18.7 µM for hCA VII, respectively. The nature of the spacer between the two histamine/spinaceamine units of these molecules was the main contributor to the diverse activating efficacy, with a very different fine tuning for the diverse isoforms. As CA activators recently emerged as interesting agents for enhancing cognition, in the management of CA deficiencies, or for therapy memory and artificial tissues engineering, our compounds may be considered as candidates for such applications.

Activation Studies of the γ-Carbonic Anhydrases from the Antarctic Marine Bacteria Pseudoalteromonas haloplanktis and Colwellia psychrerythraea with Amino Acids and Amines

The γ-carbonic anhydrases (CAs, EC 4.2.1.1) present in the Antarctic marine bacteria Pseudoalteromonas haloplanktis and Colwellia psychrerythraea, herein referred to as PhaCA and CpsCA, respectively, were investigated for their activation with a panel of 24 amino acids and amines. Both bacteria are considered Antarctic models for the investigation of photosynthetic and metabolic pathways in organisms adapted to live in cold seawater. PhaCA was much more sensitive to activation by these compounds compared to the genetically related enzyme CpsCA. The most effective PhaCA activators were d-Phe, l-/d-DOPA, l-Tyr and 2-pyridyl-methylamine, with the activation constant K_A values of 0.72–3.27 µM. d-His, l-Trp, d-Tyr, histamine, dopamine, serotonin anddicarboxylic amino acids were also effective activators of PhaCA, with K_A values of 6.48–9.85 µM. CpsCA was activated by d-Phe, d-DOPA, l-Trp, l-/d-Tyr, 4-amino-l-Phe, histamine, 2-pyridyl-methylamine and l-/d-Glu with K_A values of 11.2–24.4 µM. The most effective CpsCA activator was l-DOPA (K_A of 4.79 µM). Given that modulators of CAs from Antarctic bacteria have not been identified and investigated in detail for their metabolic roles to date, this research sheds some light on these poorly understood processes.

Activation Studies of the β-Carbonic Anhydrase from the Pathogenic Protozoan Entamoeba histolytica with Amino Acids and Amines

The β-carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic protozoan Entamoeba histolytica, EhiCA, was investigated for its activation with a panel of natural and non-natural amino acids and amines. EhiCA was potently activated by D-His, D-Phe, D-DOPA, L- and D-Trp, L- and D-Tyr, 4-amino-L-Tyr, histamine and serotonin, with K_As ranging between 1.07 and 10.1 µM. The best activator was D-Tyr (K_A of 1.07 µM). L-Phe, L-DOPA, L-adrenaline, L-Asn, L-Asp, L-Glu and L-Gln showed medium potency activation, with K_As of 16.5–25.6 µM. Some heterocyclic- alkyl amines, such as 2-pyridyl-methyl/ethyl-amine and 4-(2-aminoethyl)-morpholine, were devoid of EhiCA activating properties with K_As > 100 µM. As CA activators have poorly been investigated for their interaction with protozoan CAs, our study may be relevant for an improved understanding of the role of this enzyme in the life cycle of E. histolytica.

α-Carbonic anhydrases are strongly activated by spinaceamine derivatives

A series of 4-substituted-spinaceamine (4,5,6,7-tetrahydro-imidazolo[4,5-c]pyridine) were prepared from histamine and aromatic aldehydes Schiff bases, and investigated as activators of four human (h) carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic hCA I, II and VII, and the membrane-associated hCA IV. All isoforms were effectively activated by the new derivatives, and the nature of the moiety in position 4 of the bicyclic system was the factor influencing activation properties against all isoforms. For hCA I, these compounds showed K_As in the range of 2.52-21.5 µM, the most effective activator being 4-(2-hydroxyphenyl)-spinaceamine. For hCA II the activation constants ranged between 0.60 and 17.2 µM, with 4-(2,3,5,6-tetrafluorophenyl)- spinaceamine the best activator. Affinity for hCA IV was in the range of 0.52-63.8 µM, and the same compound as for hCA II was the most effective activator. The most sensitive isoform for activation was the brain-associated hCA VII, for which K_As in the range of 82 nM-4.26 µM were observed. Effective hCA VII activators were the (2-bromophenyl)-, 2,3,5,6-tetrafluorophenyl- and furyl-substituted spineaceamines (K_As of 82-95 nM). As CA activators may have pharmacologic applications in various fields, this work provides interesting derivatives for further studies.